Signature: 'John Duke of Marlborough / By Wm. Grimaldi. / 1806'Inscription: 'His Grace the first / Duke of Marlborough / Painted on Enamel by W. Grimaldi / Enamel painter to His royal Highness / the Prince of Wales. / and their / Royal Highnesses the Duke and Duchess of York. / No. 2 Albermarle Street'